1. Field of the Invention
This invention relates to a heat wave shielding lamination, and more particularly to an improved heat wave shielding lamination comprising a plurality of thin layers laminated on the surface of a visible light transparent substrate.
2. Description of the Prior Art
Progress is being made in the development and practical application of heat wave shielding laminations consisting of thin layers of visible light transmitting material of a high refractive index alternating with those of a low refractive index formed on the surface of a visible light transparent substrate of glass or plastic. Because of their excellent transparency to visible light and their outstanding heat wave reflection characteristics, such heat wave shielding laminations are expected to be widely used on the window glass of automobiles or of buildings and in a wide range of other fields.
However, a drawback with the conventional heat wave shielding laminations has been that they did not provide the abrasion-resistance required for practical application, and because of this efforts to apply conventional heat wave shielding laminations have been extremely limited to such uses as heat shields in electronic copying machines and other such applications where the conditions of use are not so stringent. It has not been possible to apply such laminations to the windows of automobiles or of buildings owing to their lack of sufficient abrasion-resistance. For the same reason it was not possible to apply such laminations to plastic substrate materials.
Specifically, to use such heat wave shielding laminations for the windows of automobiles, they are required to pass the Taber abrasion test, one of the durability tests stipulated by JIS for automobile window glass. Evaluation of the abrasion resistance is on the basis of the haze value obtained after the test, and it is laid down in the JIS standard that the amount of abrasion measured thus must not exceed 2%.
However, in the actual testing of conventional heat wave shielding laminations interlayer peeling occurred at the interface between the high-refraction and low-refraction films, resulting in haze values in excess of 2% and therefore precluding the use of such laminations for the windows of automobiles.
Furthermore, in order to improve their abrasion-resistance conventional heat wave shielding laminations, together with their glass substrate, were subjected to heat treatment at high temperatures of around 500.degree.-600.degree. C. or more. However, such high-temperature heat treatment could not be applied to the window glass of automobiles, to spectacle or camera lenses or to substrates of plastic, and this formed an obstacle to the practical utilization of heat wave shielding laminations.